Content delivery networks (CDNs) are interconnected systems of servers that can rapidly and cost effectively deliver a variety of digital content to numerous end points, such as web browsers, mobile devices, set-top boxes and gaming consoles, via the Internet. CDNs include large distributed systems of servers located in multiple data centers in the Internet. CDN nodes are typically deployed in multiple different locations, often across multiple different backbones. The number of nodes and servers of a CDN varies, depending on the CDN's architecture. CDNs serve a substantial portion of content on the Internet, including text, graphics, Uniform Resource Locators (URLs), scripts, media files, software, documents, applications, social networks, and streaming media.
For serving content via streaming media, CDNs may, for example, use Hypertext Transfer Protocol (HTTP) Live Streaming (HLS). HLS is a HTTP-based media streaming communications protocol that involves breaking the media stream into a sequence of file downloads. Each file may be downloaded as one portion of a transport stream. Each downloaded file may be played in sequence to present a continuous media stream. As a given stream is played, the client may choose from multiple different alternative streams containing the same content encoded at various data rates. At the beginning of a streaming session, the client downloads a playlist file that specifies the different or alternate streams that are available.
In HLS, a given multimedia presentation is specified by a Uniform Resource Identifier (URI) that corresponds to the playlist file associated with the multimedia presentation. The playlist itself includes an ordered list of media URIs and informational tags. Each media URI refers to a media file that is a segment of a single continuous media stream. To play a stream, a client first obtains the playlist file and then obtains and plays each media file in the playlist in sequence.
Over-the-top (OTT) services involve services, which deliver audio, video, data, voice and other media, that ride on top of an existing network service provided by a network operator, where the OTT services don't require any business or technology affiliations with the network operator. For example, televisions (TVs), Digital Video Disk (DVD) players and video game consoles are being built with wireless connectivity such that they can “piggyback” on an existing wireless network and pull content from the Internet. OTT services are likely to have a significant role in the proliferation of Internet television and Internet-connected TVs.